Moose is a complete object system for Perl 5.
Consider any modern object-oriented language (which Perl 5 definitely isn't).
It provides keywords for attribute declaration,
object construction,
inheritance,
and maybe more.
These keywords are part of the language,
and you don't care how they are implemented.

Moose aims to do the same thing for Perl 5 OO.
We can't actually create new keywords,
but we do offer "sugar" that looks a lot like them.
More importantly,
with Moose,
you define your class declaratively,
without needing to know about blessed hashrefs,
accessor methods,
and so on.

With Moose,
you can concentrate on the logical structure of your classes,
focusing on "what" rather than "how".
A class definition with Moose reads like a list of very concise English sentences.

Moose is built on top of Class::MOP,
a meta-object protocol (aka MOP).
Using the MOP,
Moose provides complete introspection for all Moose-using classes.
This means you can ask classes about their attributes,
parents,
children,
methods,
etc.,
all using a well-defined API.
The MOP abstracts away the symbol table,
looking at @ISA vars,
and all the other crufty Perl tricks we know and love(?).

Moose is based in large part on the Perl 6 object system,
as well as drawing on the best ideas from CLOS,
Smalltalk,
and many other languages.

Yes, we know there are many, many ways to build objects in Perl 5, many of them based on inside-out objects and other such things. Moose is different because it is not a new object system for Perl 5, but instead an extension of the existing object system.

Moose is built on top of Class::MOP, which is a metaclass system for Perl 5. This means that Moose not only makes building normal Perl 5 objects better, but it also provides the power of metaclass programming.

Moose has been used successfully in production environments by many people and companies. There are Moose applications which have been in production with little or no issue now for years. We consider it highly stable and we are committed to keeping it stable.

Of course, in the end, you need to make this call yourself. If you have any questions or concerns, please feel free to email Stevan or the moose@perl.org list, or just stop by irc.perl.org#moose and ask away.

No. While Moose is very much inspired by Perl 6, it is not itself Perl 6. Instead, it is an OO system for Perl 5. Stevan built Moose because he was tired of writing the same old boring Perl 5 OO code, and drooling over Perl 6 OO. So instead of switching to Ruby, he wrote Moose :)

Stevan read Larry Wall's talk from the 1999 Linux World entitled "Perl, the first postmodern computer language" in which he talks about how he picked the features for Perl because he thought they were cool and he threw out the ones that he thought sucked. This got him thinking about how we have done the same thing in Moose. For Moose, we have "borrowed" features from Perl 6, CLOS (LISP), Smalltalk, Java, BETA, OCaml, Ruby and more, and the bits we didn't like (cause they sucked) we tossed aside. So for this reason (and a few others) Stevan has re-dubbed Moose a postmodern object system.